[bug] drillthrough requests calc values from API

When I click on a cell to open the drillthrough view with a calculated value, the client sends the calculated value in the select request to the backend. An example is here https://jsfiddle.net/tx6ca4ez/2/.  You can see "example_calc_value" is sent to the API but this isn't a column the API doesn't have knowledge about.   While the example API seems to just filter out the field, my API implementation doesn't and throws an error.  

Would you be able to update the client to not send calculated values in the "fields" list in the select request?  I can filter these out on the backend but ideally I don't need to do that.  If I start filtering these out, the client might send a non calculated field that actually expects data to be returned and I would just silently filter it out.  Since the API doesn't do anything with these calculated fields in the "select" request, having the client not send them at all seems to make the most sense.

Thanks,

Brian